title: The two functional enoyl-acyl carrier protein reductases of Enterococcus faecalis do not mediate triclosan resistance.
abstract: Enoyl-acyl carrier protein (enoyl-ACP) reductase catalyzes the last step of the elongation cycle in the synthesis of bacterial fatty acids. The Enterococcus faecalis genome contains two genes annotated as enoyl-ACP reductases, a FabI-type enoyl-ACP reductase and a FabK-type enoyl-ACP reductase. We report that expression of either of the two proteins restores growth of an Escherichia coli fabI temperature-sensitive mutant strain under nonpermissive conditions. In vitro assays demonstrated that both proteins support fatty acid synthesis and are active with substrates of all fatty acid chain lengths. Although expression of E. faecalis fabK confers to E. coli high levels of resistance to the antimicrobial triclosan, deletion of fabK from the E. faecalis genome showed that FabK does not play a detectable role in the inherent triclosan resistance of E. faecalis. Indeed, FabK seems to play only a minor role in modulating fatty acid composition. Strains carrying a deletion of fabK grow normally without fatty acid supplementation, whereas fabI deletion mutants make only traces of fatty acids and are unsaturated fatty acid auxotrophs.
  
  
  OBJECTIVE
  The finding that exogenous fatty acids support growth of E. faecalis strains defective in fatty acid synthesis indicates that inhibitors of fatty acid synthesis are ineffective in countering E. faecalis infections because host serum fatty acids support growth of the bacterium.
authors.affiliation: Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms, College of Life Sciences, South China Agricultural University, Guangzhou, Guangdong, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Zhu
authors.forename: Hongkai
authors.initials: H
authors.lastname: Bi
authors.forename: Jincheng
authors.initials: J
authors.lastname: Ma
authors.forename: Zhe
authors.initials: Z
authors.lastname: Hu
authors.forename: Wenbin
authors.initials: W
authors.lastname: Zhang
authors.forename: John E
authors.initials: JE
authors.lastname: Cronan
authors.forename: Haihong
authors.initials: H
authors.lastname: Wang
mesh_terms: D000213:Acyl Carrier Protein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013293:Enterococcus faecalis / Q000737:chemistry / Q000187:drug effects* / Q000201:enzymology* / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D014260:Triclosan / Q000494:pharmacology*
chemical_list: D000213:Acyl Carrier Protein; D001426:Bacterial Proteins; D005227:Fatty Acids; D014260:Triclosan; D010088:Oxidoreductases